Process for producing Hydrocarbon conversion catalyst composition

ABSTRACT

A catalyst composition, a process for producing the composition, and a hydrotreating process for converting a hydrocarbon stream such as, for example, gasoline, to olefins and C 6  to C 8  aromatic hydrocarbons such as toluene and xylenes are disclosed. The catalyst composition comprises a zeolite, a clay, and a promoter. The process for producing the composition comprises the steps: (1) combining a zeolite with a clay and a promoter under a condition sufficient to bind the clay to the zeolite to produce a clay-bound zeolite; and (2) heating the clay-bound zeolite to produce a modified zeolite. The hydrotreating process comprises contacting a hydrocarbon stream with the catalyst composition under a condition sufficient to effect the conversion of a hydrocarbon to an olefin and a C 6  to C 8  aromatic hydrocarbon.

This application is a division of application Ser. No. 09/172,641 filedOct. 14, 1998, now U.S. Pat. No. 6,063,975, which is a division ofapplication Ser. No. 08/920,821 filed Aug. 29, 1997, now U.S. Pat. No.5,883,034.

This application is also a continuation-in-part application of Ser. No.08/890,540, filed Jul. 9, 1997 which is now U.S. Pat. No. 5,883,033.

FIELD OF THE INVENTION

This invention relates to a composition useful for converting ahydrocarbon to a C₆ to C₈ aromatic hydrocarbon and an olefin, to aprocess for producing the composition, and to a process for using thecomposition for converting a hydrocarbon to a C₆ to C₈ aromatichydrocarbon and an olefin.

BACKGROUND OF THE INVENTION

It is well known to those skilled in the art that aromatic hydrocarbonsand olefins are each a class of very important industrial chemicalswhich find a variety of uses in petrochemical industry. It is also wellknown to those skilled in the art that catalytically crackinggasoline-range hydrocarbons produces lower olefins such as, for example,propylene; and aromatic hydrocarbons such as, for example, benzene,toluene, and xylenes (hereinafter collectively referred to as BTX) inthe presence of catalysts which contain a zeolite. The product of thiscatalytic cracking process contains a multitude of hydrocarbonsincluding unconverted C₅+alkanes; lower alkanes such as methane, ethane,and propane; lower alkenes such as ethylene and propylene; C₆-C₈aromatic hydrocarbons; and C₉+aromatic compounds which contain 9 or morecarbons per molecule. Recent efforts to convert gasoline to morevaluable petrochemical products have therefore focused on improving theconversion of gasoline to olefins and aromatic hydrocarbons by catalyticcracking in the presence of zeolite catalysts. For example, agallium-promoted zeolite ZSM-5 has been used in the so-called CyclarProcess to convert a hydrocarbon to BTX.

Olefins and aromatic hydrocarbons can be useful feedstocks for producingvarious organic compounds and polymers. However, the weight ratio ofolefins to aromatic compounds produced by the conversion process isgenerally less than 50%. Additionally, a zeolite catalyst is generallydeactivated in a rather short period, especially in a high sulfur and/orhigh polyaromatic environment, because of depositions of carbonaceousmaterial, generally coke, on the surface of the catalyst. Moreover, theBTX purity in the product is generally not desirably high. Therefore,development of a catalyst and a process for converting hydrocarbons tothe more valuable olefins and BTX and for reducing coke deposition wouldbe a significant contribution to the art and to the economy.

SUMMARY OF THE INVENTION

An object of this invention is to provide a catalyst composition whichcan be used to convert a hydrocarbon to a C₆ to C₈ aromatic hydrocarbonand an olefin. Also an object of this invention is to provide a processfor producing the catalyst composition. Another object of this inventionis to provide a process which can employ the catalyst composition toconvert a hydrocarbon to an olefin and a C₆ to C₈ aromatic hydrocarbon.An advantage of the catalyst composition is that it enhances the ratioof produced olefins to BTX. Another advantage of the catalystcomposition is that it suppresses the deposition of coke during ahydrotreating process. Other objects and advantages will becomes moreapparent as this invention is more fully disclosed hereinbelow.

According to a first embodiment of the present invention, a compositionwhich can be used as a catalyst for converting a hydrocarbon or ahydrocarbon mixture to an olefin and a C₆ to C₈ aromatic hydrocarbon isprovided. The composition comprises a zeolite, a binder such as clay,and optionally at least one metal or element selected from the groupconsisting of Group IA, Group IIA, Group IIIA, Group IVA, Group VA,Group IIB, Group IIIB, Group IVB, Group VIB, of the Periodic Table ofthe Elements, CRC Handbook of Chemistry and Elements, 67th edition,1986-1987 (CRC Press, Boca Raton, Fla.), and combinations of two or morethereof.

According to a second embodiment of the present invention, a processwhich can be used for producing a catalyst composition is provided. Theprocess comprises the steps: (1) optionally contacting a zeolite withsteam whereby a steamed zeolite is formed; (2) optionally contacting azeolite or the steamed zeolite with an acid in an amount and under acondition effective to produce an acid-leached zeolite; (3) combining azeolite, which can also be the steamed zeolite or the acid-leachedzeolite, with a clay and a promoter under a condition sufficient to bindthe clay to the zeolite to produce a clay-bound zeolite; and (4)heat-treating the clay-bound zeolite to produce a modified zeolitewherein the promoter is selected from the group consisting of Group IA,Group IIA, Group IIIA, Group IVA, Group VA, Group IIB, Group IIIB, GroupIVB, Group VIB, of the Periodic Table of the Elements, CRC Handbook ofChemistry and Elements, 67th edition, 1986-1987 (CRC Press, Boca Raton,Fla.), and combinations of two or more thereof.

According to a third embodiment of the present invention, a processwhich can be used for converting a hydrocarbon or a hydrocarbon mixtureto an olefin and a C₆ to C₈ aromatic hydrocarbon is provided whichcomprises, consists essentially of, or consists of, contacting a fluidwhich comprises a hydrocarbon or a hydrocarbon mixture with a catalystcomposition, which can be the same as disclosed above in the firstembodiment of the invention, under a condition effective to convert ahydrocarbon to an olefin and an aromatic hydrocarbon containing 6 to 8carbon atoms per molecule wherein the weight ratio of the olefin toaromatic compound is enhanced.

DETAILED DESCRIPTION OF THE INVENTION

The catalyst composition of the first embodiment of the presentinvention can comprise, consist essentially of, or consist of a zeoliteand a clay. According to the present invention the weight ratio of clayto zeolite can be any ratio that can enhance the production of an olefinfrom a hydrocarbon and can be in the range of from about 1:20 to about20:1, preferably about 1:10 to about 10:1, and most preferably about 1:7to about 5:1. The composition can also comprise, consist essentially of,or consist of, a zeolite, a clay, and a promoter selected from the groupconsisting of Group IA, Group IIA, Group IIIA, Group IVA, Group VA,Group IIB, Group IIIB, Group IVB, Group VIB, of the Periodic Table ofthe Elements, and combinations of two or more thereof. The term“promoter” refers to a compound, a metal, or an element that, whenincorporated in a zeolite, can suppress coke formation, or enhanceolefin production, or both, in a hydrocarbon conversion process. Theterm “metal or element” used herein also includes a compound of themetal or element. For the interest of simplicity, any references to“metal” in the application, unless otherwise indicated, will include theelements listed above and a compound of any of the elements.

The weight ratio of each promoter to zeolite can be any ratio as long asthe ratio can suppress the coke formation during a hydrocarbonconversion process. Generally, the ratio can be in the range of fromabout 0.01:1 to about 1: 1, preferably about 0.03:1 to about 1:1, andmost preferably 0.04:1 to 0.5:1. The composition can also comprise,consist essentially of, or consist of a zeolite, a clay, a promoter, anda binder. The weight of the binder generally can be in the range of fromabout I to about 50, preferably about 5 to about 40, and most preferably5 to 35 grams per 100 grams of the composition.

Any binders known to one skilled in the art for use with a zeolite aresuitable for use herein. Examples of suitable binders include, but arenot limited to, aluminas such as for example α-alumina and γ-alumina;silicas; alumina-silica; aluminum phosphate; aluminum chlorohydrate; andcombinations of two or more thereof. Because these binders are wellknown to one skilled in the art, description of which is omitted herein.The presently preferred binder, if employed, is alumina because it isreadily available.

The composition can further be characterized by having the followingphysical characteristics: a surface area as determined by the BET methodusing nitrogen in the range of from about 300 to about 600, preferably350 to 500 m²/g; a pore volume in the range of from about 0.4 to about0.8, preferably about 0.5 to about 0.75, and most preferably 0.6 to 0.75ml/g; an average pore diameter in the range of from about 70 to about300, preferably about 100 to about 250, and most preferably 125 to 200Å; and a porosity of more than about 50%.

Any clay that can enhance the production of olefins in the conversion ofa hydrocarbon to an aromatic compound can be used. Examples of claysinclude, but are not limited to, kaolinite, halloysite, vermiculite,chlorite, attapulgite, smectite, montmorillonite, illite, saconite,sepiolite, palygorskite, and combinations of any two or more thereof.The presently preferred clay is montmorillonite which is commonlypresent in bentonite.

According to the present invention, any compound containing a metal orelement selected from the group consisting of Group IA, Group IIA, GroupIIIA, Group IVA, Group VA, Group IIB, Group IIIB, Group IVB, Group VIB,of the Periodic Table of the Elements, and combinations of two or morethereof can be used as promoter. Illustrated hereinbelow are someexamples of suitable promoters.

Any zinc-containing compounds which can, when incorporated into azeolite, reduce coke formation in a hydrocarbon conversion reaction canbe used in the present invention. Examples of suitable zinc-containingcompounds include, but are not limited to, zinc titanate, zinc silicate,zinc borate, zinc fluorosilicate, zinc fluorotitanate, zinc molybdate,zinc chromate, zinc tungstate, zinc zirconate, zinc chromite, zincaluminate, zinc phosphate, zinc acetate dihydrate, diethylzinc, zinc2-ethylhexanoate, and combinations of two or more thereof.

Also any titanium-containing compounds that, when incorporated into azeolite, reduce coke formation in a hydrocarbon conversion reaction canbe employed in the invention. Examples of suitable titanium-compoundsinclude, but are not limited to, titanium zinc titanate, lanthanumtitanate, titanium tetramides, titanium tetramercaptides, titaniumchloride, titanium oxalate, zinc titanate, tetraisopropyl titanate,tetra-n-butyl titanate, tetrakis(2-ethylhexyl) titanate, titaniumtetramethoxide, titanium dimethoxydiethoxide, titanium tetraethoxide,titanium tetra-n-butoxide, titanium tetrahexyloxide, titaniumtetradecyloxide, titanium tetraeicosyloxide, titaniumtetracyclohexyloxide, titanium tetrabenzyloxide, titaniumtetra-p-tolyloxide, titanium tetraphenoxide, and combinations of two ormore thereof.

Similarly, examples of suitable magnesium-containing compounds include,but are not limited to, magnesium silicate, magnesium nitrate, magnesiumacetate, magnesium acetylacetoante, magnesium chloride, magnesiummolybdate, magnesium hydroxide, magnesium sulfate, magnesium sulfide,magnesium titanate, magnesium tungstate, magnesium formate, magnesiumbromide, magnesium bromide diethyl etherate, magnesium fluoride, dibutylmagnesium, magnesium methoxide, Mg(OC₂H₅)₂, Mg(OSO₂CF₃)₂, dipropylmagnesium, and combinations of two or more thereof.

Generally any silicon-containing compounds which are effective tosuppress coke formation on a zeolite in a hydrocarbon conversion processcan be used in the present invention. Examples of suitablesilicon-containing compounds can have a formula of(R)(R)(R)Si—(—O_(m)Si(R)(R))_(n)R wherein each R can be the same ordifferent and is independently selected from the group consisting ofhydrogen, alkyl radicals, alkenyl radicals, aryl radicals, alkarylradicals, aralkyl radicals, and combinations of any two or more thereof;m is 0 or 1; and n is 1 to about 10 wherein each radical can contain 1to about 15, preferably 1 to about 10 carbon atoms per radical. Specificexamples of such compounds include, but are not limited to,silicon-containing polymers such as poly(phenylmethylsiloxane),poly(phenylethylsiloxane), poly(phenylpropylsiloxane),hexamethyldisiloxane, decamethyltetrasiloxane,diphenyltetramethyldisiloxane, and combinations of any two or morethereof. Other silicon-containing compounds include organosilicates suchas, for example, tetraethyl orthosilicate. A number of well knownsilylating agents such as trimethylchlorosilane,chloromethyldimethylchlorosilane, N-trimethylsilylimidazole,N,O-bis(trimethylsilyl)acetimide,N-methyl-N-trimethylsilyltrifluoroacetamide,t-butyldimethylsilylimidazole, N-trimethylsilylacetamide,methyltrimethoxysilane, vinyltriethoxysilane, ethyltrimethoxysilane,propyltrimethoxysilane, (3,3,3-trifluoropropyl)trimethoxysilane,[3-(2-aminoethyl)aminopropyl]trimethoxysilane,cyanoethyltrimethoxysilane, aminopropyltriethoxysilane,phenyltrimethoxysilane, (3-chloropropyl)trimethoxysilane,(3-mercaptopropyl)trimethoxysilane, (3-glycidoxypropyl)trimethoxysilane,vinyltris(β-methoxyethoxy)silane,(γ-methacryloxypropyl)trimethoxysilane, vinylbenzyl cationic silane,(4-aminopropyl)triethoxysilane,[γ-(β-aminoethylamino)propyl]trimethoxysilane,(γ-glycidoxypropyl)trimethoxysilane,[β-(3,4-epoxycyclohexyl)ethyl]trimethoxysilane,(β-mercaptoethyl)trimethoxysilane, (γ-chloropropyl)trimethoxysilane, andcombinations of any two or more thereof can also be employed. Thepresently preferred silicon-containing compounds are tetraethylorthosilicate and poly(phenylmethyl) siloxane.

Similarly, any phosphorus-containing compounds that, when impregnatedonto or incorporated into a metal oxide-promoted alumina can beconverted into a phosphorus oxide, are capable of reducing cokedeposition on a metal oxide-promoted alumina, as compared to the use ofthe metal oxide-promoted alumina only, can be used in the presentinvention. Examples of suitable phosphorus-containing compounds include,but are not limited to, phosphorus pentoxide, phosphorus oxychloride,phosphoric acid, phosphites P(R)₃ such as triethyl phosphite P(OR)₃,phosphates P(O)(OR)₃ such as triethyl phosphate and tripropyl phosphate,P(O)(R)₃, phosphines P(R)₃, and combinations of any two or more thereofwherein R is the same as that disclosed above.

Examples of suitable boron-containing compounds include, but are notlimited to boric acid, borane-ammonium complex, boron trichloride, boronphosphate, boron nitride, triethyl borane, trimethyl borane, tripropylborane, trimethyl borate, triethyl borate, tripropyl borate, trimethylboroxine, triethyl boroxine, tripropyl boroxine, and combinations of anytwo or more thereof.

Similarly, examples of suitable tin-containing compounds include, butare not limited to, stannous acetate, stannic acetate, stannous bromide,stannic bromide, stannous chloride, stannic chloride, stannous oxalate,stannous sulfate, stannic sulfate, stannous sulfide, and combinations ofany two or more thereof.

Similarly, examples of suitable zirconium-containing compounds include,but are not limited to, zirconium acetate, zirconium formate, zirconiumchloride, zirconium bromide, zirconium butoxide, zirconiumtert-butoxide, zirconium chloride, zirconium citrate, zirconiumethoxide, zirconium methoxide, zirconium propoxide, and combinations ofany two or more thereof.

Suitable molybdenum-containing compounds include, but are not limitedto, molybdenum chloride, molybdenum acetate, molybdenum fluoride,molybdenum oxychloride, molybdenum sulfide, ammonium heptamolybdate andcombinations of two or more thereof.

Examples of suitable germanium-containing compounds include, but are notlimited to, germanium chloride, germanium bromide, germanium ethoxide,germanium fluoride, germanium iodide, germanium methoxide, andcombinations of any two or more thereof.

Examples of suitable indium-containing compounds include, but are notlimited to indium acetate, indium bromide, indium chloride, indiumfluoride, indium iodide, indium nitrate, indium phosphide, indiumselenide, indium sulfate, and combinations of any two or more thereof.

Examples of suitable lanthanum-containing compounds include, but are notlimited to, lanthanum acetate, lanthanum carbonate, lanthanum octanoate,lanthanum fluoride, lanthanum chloride, lanthanum bromide, lanthanumiodide, lanthanum nitrate, lanthanum perchlorate, lanthanum sulfate,tanthanum titanate, and combinations of any two or more thereof.

Examples of suitable chromium containing compounds include, but are notlimited to, chromium acetate, chromium acetylacetonate, chromiumchloride, chromium fluoride, chromium hexacarbonyl, chromium nitrate,chromium nitride, chromium 2,4-pentanedionate, chromium perchlorate,chromium potassium sulfate, chromium sulfate, chromium telluride, andcombinations of two or more thereof.

Other suitable promoter compounds include, but are not limited to,sodium acetate, sodium acetylacetonate, sodium bromide, sodium iodide,sodium nitrate, sodium sulfate, sodium sulfide, potassium acetate,potassium acetylacetonate, potassium bromide, potassium chloride,potassium nitrate, potassium octanoate, potassium phosphate, potassiumsulfate, tungsten bromide, tungsten chloride, tungsten hexacarbonyl,tungsten oxychloride, tungsten sulfide, tungstic acid, and combinationsof any two or more thereof.

Any commercially available zeolite which can catalyze the conversion ofa hydrocarbon to an aromatic compound and an olefin can be employed inthe present invention. Examples of suitable zeolites include, but arenot limited to, those disclosed in Kirk-Othmer Encyclopedia of ChemicalTechnology, third edition, volume 15 (John Wiley & Sons, New York, 1991)and in W. M. Meier and D. H. Olson, “Atlas of Zeolite Structure Types,”pages 138-139 (Butterworth-Heineman, Boston, Mass., 3rd ed. 1992).Optionally a zeolite can be steam—and/or acid—treated before using thepresent invention. The presently preferred zeolites are those havingmedium pore sizes and having the physical characteristics disclosedabove. ZSM-5 and similar zeolites that have been identified as having aframework topology identified as MFI are particularly preferred becauseof their shape selectivity.

The composition of the present invention can be prepared by combining azeolite, a clay, a promoter, and optionally a binder in the weightratios or percent disclosed above under any conditions sufficient toeffect the production of such a composition.

According to the present invention, a zeolite, preferably a ZSM-5zeolite, a clay, a promoter, and optionally binder can be well mixed atabout 15 to about 100° C. under atmospheric pressure, generally in aliquid such as water or a hydrocarbon, by any means known to one skilledin the art such as stirring, blending, kneading, or extrusion, followingwhich the resulting mixture can be dried in air at a temperature in therange of from about 20 to about 800° C., for about 0.5 to about 50 hoursunder any pressures that accommodate the temperatures, preferably underatmospheric pressure. Thereafter, the dried, zeolite-binder mixture canbe further heat-treated at a temperature in the range of from about 200to 1000° C., preferably about 250 to about 750° C., and most preferably350 to 650° C. for about 1 to about 30 hours to prepare the presentcomposition. The heat treatment can be carried out by air calcination orsteam.

Generally a zeolite, before a binder is combined with the zeolite, canalso be calcined under similar conditions to remove any contaminants, ifpresent, to prepare a calcined zeolite.

A zeolite, whether it has been calcined or contains a binder, can alsobe treated with steam. The treatment of a zeolite, which can contain abinder, with steam can be carried out in any suitable container orvessel known to one skilled in the art at about 100° C. to about 1000°C. for about 1 to about 30 hours under any pressure that can accommodatethe temperatures to produce a steamed zeolite.

A zeolite, whether it has been steamed or not, can be treated with anacid before the preparation of the present composition. Generally, anyorganic acids, inorganic acids, or combinations of any two or morethereof can be used in the process of the present invention so long asthe acid can reduce the aluminum content in the zeolite. The acid canalso be a diluted aqueous acid solution. Examples of suitable acidsinclude, but are not limited to sulfuric acid, hydrochloric acid, nitricacid, phosphoric acid, formic acid, acetic acid, oxalic acid,trifluoroacetic acid, trichloroacetic acid, p-toluenesulfonic acid,methanesulfonic acid, partially or fully neutralized acids wherein oneor more protons have been replaced with, for example, a metal(preferably an alkali metal) or ammonium ion, and combinations of anytwo or more thereof. Examples of partially or fully neutralized acidsinclude, but are not limited to, sodium bisulfate, sodium dihydrogenphosphate, potassium hydrogen tartarate, ammonium sulfate, ammoniumchloride, ammonium nitrate, and combinations thereof.

Any methods known to one skilled in the art for treating a solidcatalyst with an acid can be used in the acid treatment of the presentinvention. Generally, a zeolite material, whether or not it contains abinder, or has been steamed, can be suspended in an acid solution. Theconcentration of the zeolite in the acid solution can be in the range offrom about 0.01 to about 700, preferably about 0.1 to about 600, morepreferably about 1 to about 550, and most preferably 5 to 500 grams perliter. The amount of acid required is the amount that can maintain thesolution in acidic pH during the treatment. Preferably the initial pH ofthe acid solution containing a zeolite is adjusted to lower than about7, preferably lower than about 6. Upon the pH adjustment of thesolution, the solution can be subjected to a treatment at a temperaturein the range of from about 30° C. to about 200° C., preferably about 50°C. to about 150° C., and most preferably 70° C. to 120° C. for about 10minutes to about 30 hours, preferably about 20 minutes to about 25hours, and most preferably 30 minutes to 20 hours. The treatment can becarried out under a pressure in the range of from about 1 to about 10atmospheres (atm), preferably about I atm so long as the desiredtemperature can be maintained. Thereafter, the acid-treated zeolitematerial can be washed with running water for 1 to about 60 minutesfollowed by drying, at about 50 to about 1000, preferably about 75 toabout 750, and most preferably 100 to 650° C. for about 0.5 to about 15,preferably about 1 to about 12, and most preferably 1 to 10 hours, toproduce an acid-leached zeolite. Any drying method known to one skilledin the art such as, for example, air drying, heat drying, spray drying,fluidized bed drying, or combinations of two or more thereof can beused.

The dried, acid-leached zeolite can also be further washed, if desired,with a mild acid solution such as, for example, ammonium nitrate whichis capable of maintaining the pH of the wash solution in acidic range.The volume of the acid generally can be the same volume as thatdisclosed above. The mild acid treatment can also be carried out undersubstantially the same conditions disclosed in the acid treatmentdisclosed above. Thereafter, the resulting solid can be washed and driedas disclosed above.

It should be noted that, a zeolite can be acid-leached before it istreated with steam.

The dried, acid-leached zeolite, whether it has been further washed witha mild acid or not, can be either heated with steam or calcined, ifdesired, under a condition known to those skilled in the art. Generallysuch a condition can include a temperature in the range of from about250 to about 1,000, preferably about 350 to about 750, and mostpreferably 450 to 650° C. and a pressure in the range of from about 0.5to about 50, preferably about 0.5 to about 30, and most preferably 0.5to 10 atmospheres (atm) for about 1 to about 30 hours, preferably about2 to about 20 hours, and most preferably 3 to 15 hours.

A zeolite, a calcined zeolite, or a calcined zeolite-binder mixture, canbe treated with a compound containing an exchangeable ammonium ion toprepare an ammonium-exchanged zeolite. Whether a zeolite is calcined orcontains a binder, the process or treatment in the second embodiment isthe same for each. For the interest of brevity, only a zeolite isdescribed hereinbelow. Examples of suitable ammonium-containingcompounds include, but are not limited to, ammonium sulfate, ammoniumchloride, ammonium nitrate, ammonium bromide, ammonium fluoride, andcombinations of any two or more thereof. Treatment of the zeolitereplaces the original ions such as, for example, alkali or alkalineearth metal ions of the zeolite, with predominantly ammonium ions.Techniques for such treatment are well known to one skilled in the artsuch as, for example, ion exchange of the original ions. For example, azeolite can be contacted with a solution containing a salt of thedesired replacing ion or ions.

Generally, a zeolite can be suspended in an aqueous solution of anammonium-containing compound. The concentration of the zeolite in theaqueous solution can be in the range of from about 0.01 to about 800,preferably about 0.1 to about 500, more preferably about 1 to about 400,and most preferably 5 to 100 grams per liter. The amount of theammonium-containing compound required depends on the amount of theoriginal ion(s) to be exchanged. Upon the preparation of the solution,the solution can be subject to a temperature in the range of from about30° C. to about 200° C., preferably about 40° C. to about 150° C., andmost preferably 50° C. to 125° C. for about 1 to about 100 hours,preferably about 1 to about 50 hours, and most preferably 2 to 25 hoursdepending on desired degrees of ion exchange. The treatment can becarried out under a pressure in the range of from about 1 to about 10atmospheres (atm), preferably about 1 atm or any pressure that canmaintain the required temperature. Thereafter, the treated zeolite canbe washed with running water for 1 to about 60 minutes followed bydrying and calcining to produce calcined hydrogen-form zeolite. For thepreparation of a calcined zeolite or zeolite-binder the drying andcalcining processes can be carried out substantially the same as thosedisclosed above.

Generally, the ammonium-exchanged zeolite becomes hydrogen exchangedupon calcination or high temperature treatment such that a predominantproportion of its exchangeable cations are hydrogen ions. Theabove-described ion exchange of exchangeable ions in a zeolite is wellknown to one skilled in the art, therefore, the description of which isomitted herein for the interest of brevity.

In the second embodiment of the invention, a zeolite or a zeolite-bindermixture, which could have been steamed and/or acid-leached, in a desiredionic form, regardless whether calcined or not, can be combined with aclay and a promoter by the process disclosed above for producingzeolite-binder mixture to produce the composition of the invention. Thecomposition can also be produced by contacting a zeolite and clay with apromoter compound, in a solution or suspension, under a condition knownto those skilled in the art to incorporate a promoter compound into azeolite. Because the methods for incorporating or impregnating apromoter compound into a zeolite a solid composition such as, forexample, impregnation by incipient wetness method, are well known tothose skilled in the art, the description of which is also omittedherein for the interest of brevity.

The composition of the invention then can be, if desired, pretreatedwith a reducing agent before being used in a transalkylation orhydrodealkylation process for converting a hydrocarbon to an olefin andan aromatic hydrocarbon. The presently preferred reducing agent is ahydrogen-containing fluid which comprises molecular hydrogen (H₂) in therange of from 1 to about 100, preferably about 5 to about 100, and mostpreferably 10 to 100 volume %. The reduction can be carried out at atemperature, in the range of from about 250° C. to about 800° C. forabout 0.1 to about 10 hours preferably about 300° C. to about 700° C.for about 0.5 to about 7 hours, and most preferably 350° C. to 650° C.for 1 to 5 hours. The treatment with a reducing agent can also becarried out in-situ in a reactor which is used for a hydrocarbonconversion process.

According to the third embodiment of the present invention, a processuseful for converting a hydrocarbon or a hydrocarbon mixture to amixture rich in olefins and C₆ to C₈ aromatic hydrocarbons comprises,consists essentially of, or consists of contacting a fluid streamcomprising a hydrocarbon or hydrocarbon mixture which can compriseparaffins, olefins, naphthenes, and aromatic compounds with a catalystcomposition under a condition sufficient to effect the conversion of ahydrocarbon mixture to a mixture rich in olefins and C₆ to C₈ aromatichydrocarbons or to enhance the weight ratio of olefins (ethylene andpropylene) to the C₆ to C₈ aromatic compounds. The fluid stream alsocomprises a diluent selected from the group consisting of carbondioxide, nitrogen, helium, carbon monoxide, steam, hydrogen, andcombinations of two or more thereof. The presently preferred diluentsare nitrogen and carbon dioxide for they are readily available andeffective. The catalyst composition can be the same as that disclosed inthe first embodiment of the invention and can be produced by the secondembodiment of the invention. The weight ratio of the diluent to thehydrocarbon is in the range of from about 0.01:1 to about 10:1,preferably about 0.05:1 to about 5:1, and most preferably 0.1:1 to about2:1.

The term “fluid” is used herein to denote gas, liquid, vapor, orcombinations thereof. The term “hydrocarbon” is generally referred to,unless otherwise indicated, as one or more hydrocarbons having fromabout 4 carbon atoms to about 30 carbon atoms, preferably about 5 toabout 20 carbon atoms, and most preferably 5 to 16 carbon atoms permolecule. The term “enhance or enhanced” refers to an increased weightratio of olefins to BTX employing the catalyst composition as comparedto employing only a zeolite such as commercially available ZSM-5.Examples of a hydrocarbon include, but are not limited to butane,isobutane, pentane, isopentane, hexane, isohexane, cyclohexane, heptane,isoheptane, octane, isooctane, nonane, decane, undecane, dodecane,tridecane, tetradecane, pentadecane, hexadecane, butenes, isobutene,pentenes, hexenes, benzene, toluene, ethylbenzene, xylenes, andcombinations of any two or more thereof.

Any fluid which contains a hydrocarbon as disclosed above can be used asthe feed for the process of this invention. Generally, the fluid feedstream can also contain olefins, naphthenes (cycloalkanes), or somearomatic compounds. Examples of suitable, available fluid feeds include,but are not limited to, gasolines from catalytic oil cracking processes,pyrolysis gasolines from thermal cracking of saturated hydrocarbons,naphthas, gas oils, reformates, and combinations of any two or morethereof. The origin of this fluid feed is not critical. Thoughparticular composition of a feed is not critical, a preferred fluid feedis derived from gasolines which generally contain more paraffins(alkanes) than combined content of olefins and aromatic compounds (ifpresent).

The contacting of a fluid feed stream containing a hydrocarbon with thecatalyst composition can be carried out in any technically suitablemanner, in a batch or semicontinuous or continuous process, under acondition effective to convert a hydrocarbon to a C₆ to C₈ aromatichydrocarbon. Generally, a fluid stream as disclosed above, preferablybeing in the vaporized state, is introduced into an aromatizationreactor having a fixed catalyst bed, or a moving catalyst bed, or afluidized catalyst bed, or combinations of any two or more thereof byany means known to one skilled in the art such as, for example,pressure, meter pump, and other similar means. Because an aromatizationreactor and aromatization are well known to one skilled in the art, thedescription of which is omitted herein for the interest of brevity. Thecondition can include a weight hourly space velocity of the fluid streamin the range of about 0.01 to about 100, preferably about 0.05 to about50, and most preferably 0.1 to 30 g feed/g catalyst/hour. Generally, thepressure can be in the range of from about 0 to about 1000 psig,preferably about 0 to about 200 psig, and most preferably 0 to 50 psig,and the temperature is about 250 to about 1000° C., preferably about 350to about 750° C., and most preferably 450 to 650° C.

The process effluent generally contains a light gas fraction comprisinghydrogen and methane; a C₂-C₃ fraction containing ethylene, propylene,ethane, and propane; an intermediate fraction including non-aromaticcompounds higher than 3 carbon atoms; and a BTX aromatic hydrocarbonsfraction (benzene, toluene, ortho-xylene, meta-xylene and para-xylene).Generally, the effluent can be separated into these principal fractionsby any known methods such as, for example, fractionation distillation.Because the separation methods are well known to one skilled in the art,the description of which is omitted herein. The intermediate fractioncan be recycled to an aromatization reactor described above, methane,ethane, and propane can be used as fuel gas or as a feed for otherreactions such as, for example, in a thermal cracking process to produceethylene and propylene. The olefins can be recovered and furtherseparated into individual olefins by any method known to one skilled inthe art. The individual olefins can then be recovered and marketed. TheBTX fraction can be further separated into individual C₆ to C₈ aromatichydrocarbon fractions. Alternatively, the BTX fraction can undergo oneor more reactions either before or after separation to individual C₆ toC₈ hydrocarbons so as to increase the content of the most desired BTXaromatic hydrocarbon. Suitable examples of such subsequent C₆ to C₈aromatic hydrocarbon conversions are disproportionation of toluene (toform benzene and xylenes), transalkylation of benzene and xylenes (toform toluene), and isomerization of meta-xylene and/or ortho-xylene topara-xylene.

After the catalyst composition has been deactivated by, for example,coke deposition or feed poisons, to an extent that the feed conversionand/or the selectivity to the desired ratios of olefins to BTX havebecome unsatisfactory, the catalyst composition can be reactivated byany means known to one skilled in the art such as, for example,calcining in air to burn off deposited coke and other carbonaceousmaterials, such as oligomers or polymers, preferably at a temperature ofabout 400 to about 650° C. The optimal time periods of the calciningdepend generally on the types and amounts of deactivating deposits onthe catalyst composition and on the calcination temperatures. Theseoptimal time periods can easily be determined by those possessingordinary skills in the art and are omitted herein for the interest ofbrevity.

The following examples are presented to further illustrate thisinvention and are not to be construed as unduly limiting the scope ofthe present invention.

EXAMPLE I

This example illustrates the preparation of catalyst composition of theinvention.

A ZSM-5 zeolite obtained from UCI (United Catalysts, Inc., Louisville,Ky.) having a product designation of T-4480 (obtained as a {fraction(1/16)} inch extrudate) was used as control catalyst (catalyst A).Zeolite T-4480 contained 30 percent by weight of alumina as binder.

A ZSM-5 zeolite obtained from CU Chemie Uetikon AG, Uetikon, Switzerlandhaving a product designation of Zeocat PZ 2/50 H (obtained as powder)was used to produce other catalyst compositions.

First, the zeolite powder was extruded, following the addition of justenough water to make a paste, to produce {fraction (1/16)} inchextrudates which were calcined at 500° C. for 3 hours (catalyst B).

Secondly, 5 g of the Zeocat zeolite powder was mixed with 5 g ofbentonite. Following the addition of just enough water to make a paste,the paste was extruded. The extrudates were heated to and at 500° C. for3 hours in a muffle furnace to produce 10 g of a zeolite containing clay(catalyst C).

In another preparation, powder PZ 2/50H zeolite (24 g) was mixed with 6g of bentonite to form a mixture followed by the addition of just enoughwater to form a paste. The paste was then extruded, dried, and calcinedat 500° C. for 3 hours to produce 30 g of a zeolite containing 20 weight% clay (catalyst D).

Still in another preparation, 10 g of PZ 2/50H was mixed with 2 g ofbentonite followed by the procedure described above for Catalyst C toproduce 12 g of a zeolite containing 16.7 weight % clay (catalyst E).

In a separate run, 20 g of PZ 2/50H powder zeolite was thoroughly mixedwith 5 g of bentonite. Following the procedure described above forproducing catalyst C, a zeolite (total 25 g) was produced (catalyst F)which contained 20 weight % clay by calculation.

Also in a separate run, 20 g of Zeocat zeolite PZ 2/50H was mixed with 5g of stannous oxide and 5 g of bentonite to form a mixture. Followingthe procedure described above for Catalyst C, a zeolite (catalyst G) (30g) containing 16.7 weight % tin and 16.7 weight % clay was produced.

Still in a separate run, 20 g of PZ 2/50H powder, 5 g of diatomaceousearth, and 5 g of bentonite were thoroughly mixed. Following theprocedure described above for the production of catalyst C, a zeolite(catalyst H) containing 14.7 weight % diatomaceous earth and 16.7 weight% clay was produced.

Catalyst AA was produced by first mixing 18 g of PZ 2/50H powder, 7 g ofbentonite, 0.6 g of zinc titanate, and enough water (21 ml) to make apaste. The paste was extruded to {fraction (1/16)} inch extrudates.Following drying the extrudates at 500° C. for 3 hours, the extrudateswere placed in a U-tube and heated with steam at 650° C. for 4 hours.

Catalyst BB was produced by first mixing 18 g of PZ 2/50H powder, 7 g ofbentonite, 0.4 g of magnesium silicate, and enough water to make apaste. The paste was then extruded to {fraction (1/16)} inch extrudateswhich were dried and heated with steam as above.

Catalyst CC was produced by first mixing 18 g of PZ 2/50H powder, 7 g ofbentonite, 0.6 g of zinc titanate, 0.5 g of magnesium silicate, and 21ml of H₂O to make a paste. The paste was extruded, dried, and heatedwith steam, as disclosed above for preparing catalysts AA and BB.

Catalyst DD was produced by first mixing 18 g of PZ 2/50H zeolite powderwith 7 g of bentonite, 0.4 g of zinc orthosilicate, and 21 ml of waterto make a paste. The paste was extruded, dried, and steamed as disclosedabove for producing catalyst AA.

Catalyst EE was produced as follows. First, 36 g of PZ 2/50H zeolite wasmixed with 14 g of bentonite, 0.8 g of zinc orthosilicate, and 47.5 mlof water to make a paste. Secondly, the paste was extruded, dried, andheated with steam as disclosed above for catalyst AA production toproduce a Zn/Si-incorporated zeolite. Thirdly, the Zn/Si-incorporatedzeolite was mixed with a triethylphosphate (TEP) solution contianing 1.2g of TEP and 20 g of n-hexane. The resulting mixture was left standingat about 20° C. for one hour to produce P-incorporated zeolite. Finally,following removal of excess hexane by evaporation, the P-incorporatedzeolite was calcined at 530° C. for 3 hours. Catalyst DD contained 2weight % phosphorus.

Catalyst FF was produced by the same produced described for catalyst EEexcept that the quantity of TEP used as 2.4 g. Catalyst FF contained 4weight % phosphorus.

EXAMPLE II

This example illustrates the use of the catalyst compositions describedin Example I as catalysts in the conversion of hydrocarbons to olefinsand BTX.

A quartz reactor tube (inner diameter 1 centimeter; length 60centimeter) was filled with a 20 centimeter bottom layer of Alundum®alumina (inert, low surface area alumina), 4.4 grams of one of thecatalysts in the middle 20 centimeter of the tube, and a 20 centimetertop layer of Alundum® alumina. The liquid feed was a gasoline obtainedfrom Phillips Petroleum Company, Bartlesville, Okla., and containedhydrocarbons shown in Table I. The liquid feed shown in Table I issummarized as: 38.7 weight percent (%) lights (C₅s and C₆s); 1.3%benzene; 5.4% toluene; 8.1% C₈ aromatics; 38.9% nonaromatics in BTXboiling range; and 25.9% heavies (C₈+). The feed was introduced into thereactor at a rate of 12 ml/hour (8.95 g/hour). The reaction temperaturewas 600° C. The reactor effluent was cooled and separated into a gaseousphase and a liquid phase by passing through a wet ice trap for liquidproduct collection and then through a wet test meter for gas volumemeasurement. The liquid was weighed hourly and analyzed on aHewlett-Packard 5890 gas chromatograph equipped with a fused silicacolumn (DB-1). The gas was sampled hourly after the ice trap andanalyzed on a Hewlett-Packard 5890 gas chromatograph using aHP-PLOT/Al₂O₃ column. The gas was also analyzed for hydrogen content ona Carle gas chromatograph using hydrocarbon trap followed by a 13Xmolecular sieve column. Both phases were analyzed by gas chromatographsat intervals of about 1 hour. The results of the runs at about 6 hoursare shown in Table II below which illustrates the production of olefinsand BTX from the Table I feed and individual catalyst compositionsproduced in Example I.

TABLE I Hydrocarbon Analysis of Catalytically Cracked Gasoline n-par-Isopar- Aro- affins affins matics Naphthenes Olefins Total C₁ 0.0000.000 0.000 0.000 0.000 0.000 C₂ 0.000 0.000 0.000 0.000 0.000 0.000 C₃0.000 0.000 0.000 0.000 0.000 0.000 C₄ 0.000 0.000 0.000 0.000 0.0180.018 C₅ 1.292 8.147 0.000 0.169 10.741 20.348 C₆ 0.749 7.164 1.2661.972 7.135 18.287 C₇ 0.740 4.576 5.354 2.746 6.483 19.899 C₈ 0.7603.234 8.120 2.531 0.830 15.475 C₉ 0.187 2.070 8.187 0.708 0.125 11.278C₁₀ 0.163 1.193 5.155 0.072 0.048 6.631 C₁₁ 0.153 0.307 3.606 0.1910.000 4.257 C₁₂ 0.115 0.974 0.768 0.088 0.000 1.946 C₁₃ 0.048 0.0000.000 0.000 0.000 0.048 C₁₄ 0.000 0.000 0.000 0.000 0.000 0.000 Total4.208 27.664 32.457 8.478 23.381 98.188 Total C₁₅+ 0.108 Total 1.704Unknowns:

TABLE II Olefins and BTX Production (weight percent in product) Productyield (wt %) % Olefin Catalyst C₂ ⁼ C₃ ⁼ BTX Total Coke BTX A(T4480) 6.46.8 42 54.7 4.4 .31 B(PZ 2/50H) 6.6 8.5 38 53.1 4.9 .40 C(PZ 2/50H +clay) 7.0 12.0 26 46.0 ND .77 D(PZ 2/50H + clay) 9.8 8.9 41 59.7 1.7 .46E(PZ 2/50H + clay) 6.6 5.4 44 56.0 1.2 .39 F(PZ 2/50H + clay) 7.8 6.8 4256.6 1.2 .35 G(PZ 2/50H + clay + SnO) 4.4 11.8 35 51.2 0.4 .46 H(PZ2/50H + clay + 9.2 12.9 30 52.1 0.8 .74 diatomaceous earth) AA(PZ2/50H + clay + 7.0 14.2 34 55.2 0.44 .62 ZnTiO₃) BB(PZ 2/50H + clay +7.0 13.6 27 47.6 0.6 .76 MgSiO₃) CC(PZ 2/50H + clay + 7.2 13.8 37 58.00.2 .54 ZnTiO₃ + MgSiO₃) DD(PZ 2/50H + clay + 7.8 11.8 40.5 60.1 0.280.48 Zn₂SiO₄) EE(PZ 2/50H + clay + 6.9 14.1 35.1 56.1 0.15 0.60Zn₂SiO₄ + TEP) FF(PZ 2/50H + clay + 5.2 13.4 24.9 43.5 0.24 0.75Zn₂SiO₄ + TEP) The WHSV (weight hourly space velocity) of gasoline feedfor each run was 2; coke was determined at the end of the reaction byremoving the catalysts from the reactor and determined with a thermalgravimetric analyzer (TGA), manufactured by TA Instruments, New Castle,Delaware; ND, not determined; TEP, triethylphosphate.

Table II shows that commercial ZSM-5 zeolite (catalyst A) containingalumina binder had a high coke yield in a gasoline aromatizationreaction. Table II also shows that a ZSM-5 zeolite (catalyst B) whichdid not contain alumina binder also had a high coke yield. Addition of abentonite clay at various concentrations (catalysts D to F)significantly lowered the amount of coke yield. Table II further showsthat increasing the ratio of zeolite to clay increased the ratio ofolefins to BTX in the product stream (catalysts C and D). The resultspresented in Table II further demonstrate that a zeolite containing clayand either stannous oxide (catalyst G) or diatomaceous earth (catalystH) not only significantly further reduced the coke formation but alsoincreased the ratio of olefms to BTX. Furthermore, Table II shows thatincorporation of ZnTiO₃ (catalyst AA), MgSiO₃ (catalyst BB), or bothZnTiO₃ and MgSiO₃ (catalyst CC) also significantly improved theproduction of olefins and reduced coke formation. Finally, Table IIshows that incorporation of Zn₂SiO₄ (catalyst DD), or both Zn₂SiO₄ andphosphorus (catalyst EE had 2 weight % P and catalyst FF contained 4weight % P), had profound effect on reduction of coke formation in anaromatization process.

EXAMPLE III

This example illustrates another embodiment of the invention.

A Zeocat zeolite (catalyst I) containing about 70 weight % PZ 2/50Hzeolite and 30% clay binder was a commercially available productobtained as {fraction (1/16)} inch extrudates.

Catalyst I (164 g) was mixed with 164 g of 37 weight % HCl and 164 g ofwater to make a suspension. The suspension was heated to and at 90° C.for 2 hours to produce a heated suspension. Following the removal ofaqueous phase by decantation from the suspension, the solid was washedwith a running tap water for about 30 minutes and then dried at 125° C.for 2 hours. The dried solid was then calcined in air in a mufflefurnace at 500° C. for 4 hours to produce 158.58 g of an acid-leachedclay-bound ZSM-5 (catalyst J).

A portion (50 g) of catalyst J was steamed (20 ml H₂O/hr) at 650° C. ina U-shape tube for 8 hours to produce an acid-leached (AL)-steamedzeolite (catalyst K).

In a separate run, 200 g of catalyst I was steamed as describedimmediately above to produce a steamed zeolite. The steamed zeolite (44g) was added to a flask containing 44 ml of H₂O and 52 ml of HCl toproduce a suspension. The suspension was heated to and then at 90° C.for 2 hours. Following removal of the aqueous phase by decantation, thesolid was washed with running tap water for about 30 minutes. The washedsolid was dried in an oven at 125° C. for 3 hours followed bycalcination in a muffle furnace at 500° C. for 3 hours to produce 40.54g of steam and acid-leached zeolite (catalyst L).

The above catalysts I, J, K, and L were employed in a gasolinearomatization process for converting gasoline to olefins and BTX usingthe procedure disclosed in Example II. The purity of BTX was determinedby dividing the area % of BTX in a GC chromatogram by the area % of allproducts in the same GC chromatogram. The results are shown in Table IIIbelow.

TABLE III Product (weight %) Pur- Ratio Ole- % Catalyst C₂ ⁼ C₃ ⁼ BTXity fins/BTX Coke I(PZ 2/50H + clay) 7.3 9.2 36 97 .46 5.6 J(AL-catalystI) 8.1 7.3 40 97 .39 1.1 K(AL-steam-catalyst I) 10.0 14.3 26 87 .93 0.4L(steam-AL-catalyst I) 10.6 13.3 30 94 .80 0.4 AL, acid-leached;AL-steam; acid-leaching followed by steam treatment; steam-AL; steamtreatment followed by acid-leaching.

Table III shows that commercially available PZ 2/50 H zeolite probablyalso contained (contaminated with) some alumina binder which could beremoved by acid-leaching. The results in Table III also show thatacid-leaching substantially decreased coke formation (catalyst J). TableIII also shows that the coke content was further reduced and the ratioof olefins to BTX was further enhanced by an acid, steam, or both,treatment. Finally, Table III shows that the treatments of zeolitecatalyst described in the invention did not adversely affect the BTXpurity.

The results shown in the above examples clearly demonstrate that thepresent invention is well adapted to carry out the objects and attainthe ends and advantages mentioned as well as those inherent therein.While modifications may be made by those skilled in the art, suchmodifications are encompassed within the spirit of the present inventionas defined by the disclosure and the claims.

What is claimed is:
 1. A process comprising: (1) combining a zeolite, aclay and a promoter selected from the group consisting of zinc titanate,magnesium silicate, zinc silicate, triethyl phosphate and combinationsof two or more thereof, under a condition sufficient to produce aclay-bound zeolite and (2) heating the clay-bound zeolite to produce amodified zeolite.
 2. A process according to claim 1 wherein the heatingstep is carried out in the presence of steam.
 3. A process according toclaim 1 wherein the weight ratio of clay to zeolite is in the range ofabout 1:20 to about 20:1 and the weight ratio of promoter to zeolite isin the range of about 0.01:1 to about 1:1.
 4. A process according toclaim 3 wherein the weight ratio of clay to zeolite is in the range ofabout 1:7 to about 5:1 and the weight ratio of promoter to zeolite is inthe range of about 0.1:1 to about 0.5:1.
 5. A process according to claim2 wherein the weight ratio of clay to zeolite is in the range of about1:20 to about 20:1 and the weight ratio of promoter to zeolite is in therange of about 0.01:1 to about 1:1.
 6. A process according to claim 5wherein the weight ratio of clay to zeolite is in the range of about 1:7to about 5:1 and the weight ratio of promoter to zeolite is in the rangeof about 0.1:1 to about 0.5:1.
 7. A process according to claim 3 whereinthe promoter is triethyl phosphate.
 8. A process according to claim 3wherein the promoter is zinc silicate.
 9. A process according to claim 3wherein the promoter is triethyl phosphate in combination with zincsilicate.
 10. A process according to claim 3 wherein the promoter iszinc titanate.
 11. A process according to claim 3 wherein the promoteris magnesium silicate.
 12. A process according to claim 3 wherein thepromoter is zinc titanate in combination with magnesium silicate.
 13. Aprocess according to claim 5 wherein the promoter is triethyl phosphate.14. A process according to claim 5 wherein the promoter is zincsilicate.
 15. A process according to claim 5 wherein the promoter istriethyl phosphate in combination with zinc silicate.
 16. A processaccording to claim 5 wherein the promoter is zinc titanate.
 17. Aprocess according to claim 5 wherein the promoter is magnesium silicate.18. A process according to claim 5 wherein the promoter is zinc titanatein combination with magnesium silicate.
 19. A process comprising: (1)combining a zeolite, a clay chosen from the group consisting ofkaolinite, halloysite, vermiculite, chlorite, attapulgite, smectite,montmorillonite, illite, saconite, sepiolite, palygorskite andcombinations of two or more thereof and a promoter selected from thegroup consisting of zinc titanate, magnesium silicate, zinc silicate,triethyl phosphate and combinations of two or more thereof, under acondition sufficient to produce a clay-bound zeolite and (2) heating theclay-bound zeolite to produce a modified zeolite wherein the weightratio of clay to zeolite is in the range of about 1:20 to about 20:1 andthe weight ratio of promoter to zeolite is in the range of about 0.01:1to about 1:1.
 20. A process comprising: (1) combining a zeolite, a claychosen from the group consisting of kaolinite, halloysite, vermiculite,chlorite, attapulgite, smectite, montmorillonite, illite, saconite,sepiolite, palygorskite and combinations of two or more thereof and apromoter selected from the group consisting of zinc titanate, magnesiumsilicate, zinc silicate, triethyl phosphate and combinations of two ormore thereof, under a condition sufficient to produce a clay-boundzeolite and (2) heating the clay-bound zeolite in the presence of steamto produce a modified zeolite wherein the weight ratio of clay tozeolite is in the range of about 1:20 to about 20:1 and the weight ratioof promoter to zeolite is in the range of about 0.01:1 to about 1:1.